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Endocrinology Flashcards

1
Q

What types of hormones are there?

A
  • modified amino acids
  • peptides (3-20 amino acids)
  • proteins (single or mulitple subunits)
  • complex chemicals e.g. steroids
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2
Q

Examples of peptide hormones?

A

Oxytocin, anti-diuretic hormone

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3
Q

Similarities between oxytocin and ADH?

A

amino acid sequence differs at only two positions

can cause some cross over effects

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4
Q

Examples of protein hormones (single subunit)?

A

Growth hormone, prolactin

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5
Q

What does growth hormone do?

A

stimulates growth, cell division and regeneration. mitogen, specific to only certain cells

also known as somatotropin or somatropin

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6
Q

What does prolactin do?

A

properties and functions resembling both a hormone and a cytokine

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7
Q

Examples of protein hormones with multiple subunits?

A

TSH, FSH, insulin

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8
Q

How must protein hormones be administered clinically?

A

not orally as they get digested

  • IV or sc injection
  • inhaled
  • depot formulations
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9
Q

HOw is adrenaline synthesised from tyrosine?

A
  1. tyrosine hydroxylase adds OH and forms dihydroxyphenylalanine (L-DOPA)
  2. DOPA decarboxylase removes carboxylate to form dopamine
  3. Dopamine b-hydroxylase forms noradrenaline
  4. phenethanolamine N-methyltransferase forms adrenaline
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10
Q

How does the body produce adrenaline only in the adrenal glands?

A

Only adrenal glands express the enzymes to progress from dopamine, and contain large amounts of N-methyltransferase

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11
Q

What type of hormone is melatonin and how is it produced?

A

modified amino acid

comes from tryptophan, via serotonin

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12
Q

Typical base structure of steroids?

A

4 ring, C17 structure

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13
Q

What is a primary endocrine organ?

A

Primary function is secretion of hormones

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14
Q

What is a secondary endocrine organ?

A

Non-endocrine primary function, but do secrete hormones

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15
Q

Examples of primary endocrine glands?

A

Pineal, hypothalamus, Pituitary, thyroid, Adrenal, parathyroid, thymus, pancreas, testes

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16
Q

Examples of secondary endocrine glands?

A

Heart, stomach, liver, kidneys, small intestine, skin

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17
Q

Function of the thymus?

A

produces thymosin, which stimulates activity of T cells and antibody production in bone marrow

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18
Q

Where are the adrenal glands and what is their function?

A

at the top of the kidneys. mainly releasing hormones in response to stress

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19
Q

What is produced in the adrenal medulla?

A

Adrenaline and noradrenaline

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20
Q

What is produced in the adrenal cortex?

A

Corticosteroids

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21
Q

What is the HPA axis?

A

Hypothalamus: releases Corticotropin releasing hormone
A. Pituitary: releases Adrenocorticotropic hormone (ACTH)
Adrenal cortex: releases cortisol

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22
Q

Functions of the ovaries?

A

secrete steroids: progesterone and oestrogen
protein hormones: inhibin and relaxin

regulated by pituitary hormones FSH and LH

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23
Q

Primary functions of the testes?

A

spermatogenesis, producing steroid hormones (testosterone)

regulated by FSH and LH

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24
Q

Functions of the placenta?

A

facilitates nutrient uptake, removal of waste products & gas exchange via the maternal blood supply

produces steroid hormones (oestrogen and progesterone) and protein hormones (chorionic gonadotropin, corticotropin releasing hormone, placental lactogenic)

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25
Endocrine functions of the heart?
Atrial natriuretic peptide (ANP) stimulates kidney to secrete more salt….. Thereby decreases excess blood volume, high BP and high blood sodium concentration
26
Endocrine functions of the GI tract?
Largest endocrine organ - over 30 hormones
27
Endocrine functions of the kidney?
Juxtaglomerular cells secrete renin (which indirectly signals adrenal cortex to produce aldosterone) also release erythropoietin signals bone marrow to increase RBC production
28
What are the three regions of the adrenal cortex (outer first)?
Zona glomerulosa, Zona fasciculata, Zona reticularis
29
What hormones are produced in the zona glomerulosa?
Mineralocorticoids e.g. aldosterone
30
What hormones are produced in the zona fasciculata?
glucocorticoids e.g. cortisol
31
What hormones are produced in the zona reticularis?
Adrenal androgens
32
Key points regarding steroid synthesis?
- steroids are not stored, they are synthesised on demand - synthesised from cholesterol - rate limiting step is first one, cholesterol to pregnenolone
33
What is the conversion of cholesterol to pregnenolone regulated by?
ACTH
34
Physiological actions of glucocorticoids?
- metabolic effects - anti-inflammatory - immunosuppressive
35
Physiological actions of mineralorticoids?
water and electrolyte balance
36
Physiological actions of adrenal androgens?
maturation and development
37
What is transcortin?
corticosteroid binding globulin - carrier binds 90% of cortisol and 60% of aldosterone does not bind to synthetic steroids
38
What is albumin?
Another transport protein, binds both natural and synthetic steroids
39
What can trigger the HPA axis pathway?
Stress
40
Mechanism of action of mineralocorticoids?
- receptors have limited tissue distribution - cause sodium reuptake and fluid resorption, leading to K loss - spironolactone is a competitie inhibitor of MC receptors
41
Examples and half lives of short acting steroids?
hydrocortisone, fludrocortisone 8-12 hours
42
Examples and half lives of intermediate acting steroids?
prednisolone 12-36 hours
43
Examples and half lives of long acting steroids?
dexamethasone, betamethasone | 36-72hours
44
Which synthetic steroids have mixed glucocorticoid and mineralocorticoid activity?
prednisolone
45
Which synthetic steroids have pure glucocorticoid activity?
dexamethasone, betamethasone, beclomethasone
46
Which synthetic steroids have mainly mineralocorticoid activity?
fludrocortisone
47
Place of steroids in addisons disease treatment?
replacement therapy for adrenal failure Hydrocortisone (GC) with or without fludrocortisone (MC) - limited side effects as mimin normal plasma concentrations
48
What is congenital adrenal hyperplasia?
- fault in steroidogenesis pathway - insufficient cortisol produced (and too many androgens) so no negative feedback on hypothalamus and pituitary - increased output of ACTH
49
How is congenital adrenal hyperplasia treated?
synthetic cortisol to provide the negative feedback limited side effects as normal plasma concentrations are mimicked
50
Mechanism of steorids used for inflammation/immunosuppression?
Reduce mediators of inflammation and immune responses inc prostaglandin, cytokines, NO, IgG, etc
51
Effects of excessive glucocoritcoid use?
- drug induced Cushing's - osteoporosis - increased risk of infection
52
What is aminoglutethimide?
inhibits several enzymes in the steroidogenesis pathway used for Cushing's, post menopausal breast cancer, prostate cancer
53
What is Metyrapone?
Inhibits 11 β-hydroxylase so reduces synthesis of gluco and mineralocorticoids - indirectly increases ACTH as less negative feedback used for: testing A. pituitary function, Cushing's, hyperaldosteronism can cause manly hair growth in women due to excess androgens
54
What is Synacthen?
synthetic peptide, ACTH analogue - stimulates synthesis and release of adrenal hormones - used to diagnose adrenal cortical insufficiency
55
Location of the hypothalamus?
just below the thalamus above the brain stem
56
Location of the pituitary gland?
in a small bony cavity below hypothalamus
57
Why can pituitary tumour early signs be visual disturbances?
can only grow upwards due to bone, so meets optic nerve
58
How does the hypothalamus link to the anterior pituitary?
parvicellular neurones - secrete regulatory hormones into the blood which travels down to AP (circulatory link)
59
How does the hypothalamus link to the posterior pituitary?
Magnocellular neurones - long axons which release hormones directly into PP (direct neuro-endocrine link)
60
Tropic effect of prolactin releasing hormone?
positive. causes AP to release prolactin, which acts on mammary development and lactation hypothetical - hasn't been proven to have an effect yet
61
Tropic effect of prolactin inhibiting hormone?
negative. inhibits release of prolactin, which acts on mammary development and lactation
62
Tropic effect of thyrotropin releasing hormone?
positive. stimulates release of TSH in AP, which causes release of thyronines in the thyroid
63
Tropic effect of corticotropin releasing hormone?
positive. stimulates release of ACTH which acts on the adrenal cortex
64
Tropic effect of growth hormone releasing hormone?
positive. stimulates release of growth hormone from AP which causes release of growth factors
65
Tropic effect of growth hormone inhibiting hormone?
negative. inhibits release of growth hormone from AP
66
Tropic effect of gonadotropin releasing hormone?
positive. stimulates release of FSH and LH from AP
67
How to remember the anterior pituitary hormones?
``` Flat Pig FSH LH ACTH TSH Pi rolactin Growth hormone ``` Flat are tropic, PiG are non tropic
68
Where are the gonadotropins synthesised and stored?
gonadotropes
69
Functions of gonadotropes?
FSH: ovaries to produce oestrogen LH: ovulation and corpus luteum growth, plus androen secretion in testes
70
What is corticotropin and where is it stored/synthesised?
ACTH - corticotropes
71
What is thyrotropin and where is it stored/synthesised?
TSH - thyrotropes
72
What is the HPT axis?
determines thyroxine secretion short loop feedback: thyroid hormones stop TSH secretion long loop feedback: thyroid hormones inhibit TRH secretion from hypothalamus
73
What are the three feedback loops for CRH/ACTH?
ultra short: CRH inhibits further secretion of CRH short: cortisol inhibits ACTH secretion long: cortisol inhibits CRH secretion
74
Structure and functions of prolactin?
- 198 amino acid chain - synthesised/stored in lactotropes - effects on breast tissue for lactation
75
Most common pituitary tumour and how is it treated?
prolactinoma: treated with dopamine receptor agonists eg. bromocriptine, cabergoline
76
Structure and functions of growth hormone?
- 191 amino acid protein | - synthesised/stored in somatotropes
77
effects of hypersecretion of growth hormone?
gigantism in children, acromegaly in adults
78
How is acromegaly treated?
Somatostatin (growth hormone inhibiting hormone)
79
Mechanism of somatostatin?
regulates production of growth hormone, and affects cell proliferation/growth via somatostatin receptors
80
Why is a synthetic analogue of somatostatin used for treatment?
longer half life (90 min vs 3) | only 8 amino acids instead of 14
81
What causes growth hormone deficiency?
- hypothalamic or pituitary tumour - GH gene mutation - head injury/infection - radiotherapy - GH resistance (Laron dwarfism) - mutations in the binding protein or receptor
82
How is growth hormone deficiency treated?
somatotropin 7 preps available, made by recombinant DNA technology, identical to human sequence
83
What is protirelin?
TRH - treatment for severe hypothyroidism (iv injection, rarely used)
84
What is gonadorelin?
GnRH - induces FSH and LH. used for endometriosis and infertility
85
What is vasopressin?
Treatment for pituitary diabetes insipidus
86
What hormones are secreted by the posterior pituitary?
oxytocin and vasopressin
87
Functions of oxytocin?
- stimulation of milk ejection - stimulation of uterinevsmooth muscle contraction at birth - establishment of matternal behaviour
88
What type of feedback loop controls oxytocin during childbirth?
Positive feedback - pressure on cervix causes release of oxytocin, which causes contraction and more pressure onthe cervix
89
When must you stop synthetic oxytocin being used in labour?
contracts lasting >90 seconds, or <2 mins apart, fetal decelerations monitor for blood pressure changes, hypertonicity of uterus and fetal heart rate
90
Functions of vasopressin?
- binds to receptors in the collecting ducts of the kidney - synthesis and insertion of aquaporins into kidney tubules - promotes reabsorption of water back into the kidenys
91
What happens in the absence of vasopressin?
collecting ducts are virtually impermeable, all water flows out as urine
92
What is diabetes insipidus?
lack of vaopressin response, leads to excessive urine production
93
What are the two types of diabetes insipidus?
- hypothalamic: insufficient vasopressin secretion. caused by trauma, infection or tumour affecting hypothalamus. treated with exogeneous vasopressin - nephrogenic: kidney is insensitive to vasopressin. caused by renal disease, receptor gene mutation or aquaporin gene mutation. treat by increasing water consumption
94
What is the pineal gland?
- 6mm, located in the epithalamus | - pinealocytes secrete melatonin, which regulates circadian rhythm. light inhibits production

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